Interleukin 12, also known as Natural Killer Cell Stimulatory Factor (NKSF) or Cytotoxic Lymphocyte Maturation Factor (CLMF), is a heterodimeric pleiotropic cytokine made up of a 40 kDa (p40) subunit and a 35 kDa (p35) subunit. IL‑12 is produced by macrophages and B lymphocytes and has been shown to have multiple effects on T cells and Natural Killer (NK) cells. Some of these IL‑12 activities include the induction of IFN‑ gamma and TNF in resting and activated T and NK cells; the enhancement of cytotoxic activity of resting NK and T cells, the stimulation of resting T cell proliferation in the presence of a comitogen; and the enhancement of NK cell proliferation. Current evidence indicates that IL‑12 is a key mediator of cellular-immunity and induces the differentiation of Th1 cells from precursor T helper cells. Based on its activities, it has been suggested that IL‑12 may have therapeutic potential as a vaccine adjuvant that promotes cellular-immunity and as an anti-tumor and anti-viral agent.
Human and mouse IL‑12 share 70% and 60% amino acid sequence identity in their p40 and p35 subunits, respectively. While mouse IL‑12 is active on both human and mouse cells, human IL‑12 is not active on murine cells. R&D Systems' recombinant mouse IL‑12 preparations were proteolytically cleaved between residues G158 and E159 of the mature p35 subunit. Thus, under reducing conditions, three bands representing the p40 subunit, the p35 R1 ‑ G158 peptide and the p35 E159 - A193 peptide can be observed in SDS-PAGE. The biological activity of this cleaved mouse IL‑12 is comparable to that of the intact human IL‑12.
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